Mac: Youtube comes with a complete set of great shortcuts, but if you're used to the Mac's media keys it's easy to go for F9 instead of the spacebar to pause a video. Tube Controller is a simple app that makes your media keys control YouTube.

With Tube Controller, when you want to start or pause a video on YouTube, hit the play button on your keyboard. If you're listening to music in iTunes, Tube Controller is smart enough to pause iTunes, and then play the YouTube video as long as YouTube is in focus. The skip buttons also work, and they fast-forward (or rewind) the video about 15 seconds. Tube Controller is a simple little app, but if you find yourself always reaching for those media keys instead of designated YouTube shortcuts it works great.